Thermoform windshield stack with integrated formable mold

ABSTRACT

A method of installing a stack of two or more lenses on a curved substrate includes placing a moldable covering on a curved substrate, the moldable covering including a stack of two or more lenses, an adhesive layer interposed between each pair of adjacent lenses from among the two or more lenses, and a sacrificial layer disposed on an outermost lens of the stack, the sacrificial layer including a sacrificial lens and a sacrificial adhesive interposed between the sacrificial lens and the outermost lens of the stack. The method may include applying heat and pressure to the sacrificial layer and peeling off the sacrificial layer to reveal the stack of two or more lenses.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application relates to and claims the benefit of U.S. ProvisionalApplication No. 62/799,880, filed Feb. 1, 2019 and entitled “ThermoformWindshield Stack With Integrated Formable Mold,” the entire contents ofwhich is expressly incorporated herein by reference.

STATEMENT RE: FEDERALLY SPONSORED RESEARCH/DEVELOPMENT

Not Applicable

BACKGROUND 1. Technical Field

The present disclosure relates generally to transparent coverings forwindows and, more particularly, to transparent coverings having multiplelenses stacked one over the other and adhered together by adhesive.

2. Related Art

There may be various advantages to affixing transparent lenses to curvedsubstrates such as windshields (also referred to as windscreens). Suchcoverings may provide protection from pitting and cracking, tinting(e.g. for privacy), thermal insulation, blocking of ultraviolet (UV)radiation, and/or decoration. A stack of such transparent lenses mayallow for easy tear-away as the outermost lens becomes dirty andobstructs the driver's vision, such as might occur in vehicles foroff-road use.

While the surface of a typical windshield usually exhibits a compoundcurvature, the transparent lenses may themselves be flat, such as in thecase of polyethylene terephthalate (PET) films manufactured in aroll-to-roll process. In order to install a flat film to a compoundcurved windshield surface, the film may be drape formed over thewindshield, e.g. by laying the film over the windshield and applyingheat to the uppermost surface to shrink or stretch the film to take theshape of the windshield. However, this process may result in unevenheating or overheating, which may cause optical distortion in the filmand may result in areas where the film is not adequately adhered to thewindshield. In addition, the efforts of the installer to apply pressureto the film with a card or squeegee may result in permanently scratchingthe visible surface during installation.

BRIEF SUMMARY

The present disclosure contemplates various systems and methods forovercoming the above drawbacks accompanying the related art. One aspectof the embodiments of the present disclosure is a method of installing astack of two or more lenses on a curved substrate. The method mayinclude placing a moldable covering on a curved substrate, the moldablecovering including a stack of two or more lenses, an adhesive layerinterposed between each pair of adjacent lenses from among the two ormore lenses, and a sacrificial layer disposed on an outermost lens ofthe stack, the sacrificial layer including a sacrificial lens and asacrificial adhesive interposed between the sacrificial lens and theoutermost lens of the stack. The method may include applying heat andpressure to the sacrificial layer and peeling off the sacrificial layerto reveal the stack of two or more lenses.

The curved substrate may be a compound curved substrate. The curvedsubstrate may be a windshield.

The sacrificial layer may be more heat resistant than the outermost lensof the stack.

The sacrificial layer may be less scratch resistant than the outermostlens of the stack.

The sacrificial lens may comprise a biaxially oriented polyethyleneterephthalate film. The biaxially oriented polyethylene terephthalatefilm may be able to withstand temperatures between room temperature and220° C. for two hours.

The sacrificial lens may comprise an opaque polyester film. Theoutermost lens of the stack may comprise a transparent polyethyleneterephthalate film.

Another aspect of the embodiments of the present disclosure is amoldable covering affixable to a curved substrate, the moldable coveringmay include a stack of two or more lenses, an adhesive layer interposedbetween each pair of adjacent lenses from among the two or more lenses,and a sacrificial layer disposed on an outermost lens of the stack, thesacrificial layer including a sacrificial lens and a sacrificialadhesive interposed between the sacrificial lens and the outermost lensof the stack, the sacrificial layer being more heat resistant than theoutermost lens of the stack.

The sacrificial lens may comprise a biaxially oriented polyethyleneterephthalate film. The biaxially oriented polyethylene terephthalatefilm may be able to withstand temperatures between room temperature and220° C. for two hours.

The sacrificial lens may comprise an opaque polyester film. Theoutermost lens of the stack may comprise a transparent polyethyleneterephthalate film.

Another aspect of the embodiments of the present disclosure is amoldable covering affixable to a curved substrate. The moldable coveringmay include a stack of two or more lenses, an adhesive layer interposedbetween each pair of adjacent lenses from among the two or more lenses,and a sacrificial layer disposed on an outermost lens of the stack, thesacrificial layer including a sacrificial lens and a sacrificialadhesive interposed between the sacrificial lens and the outermost lensof the stack, the sacrificial layer being less scratch resistant thanthe outermost lens of the stack.

The sacrificial lens may comprise a biaxially oriented polyethyleneterephthalate film. The biaxially oriented polyethylene terephthalatefilm may be able to withstand temperatures between room temperature and220° C. for two hours.

The sacrificial lens may comprise an opaque polyester film. Theoutermost lens of the stack may comprise a transparent polyethyleneterephthalate film.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other features and advantages of the various embodimentsdisclosed herein will be better understood with respect to the followingdescription and drawings, in which like numbers refer to like partsthroughout, and in which:

FIG. 1 is schematic side view of a moldable covering according to anembodiment of the present disclosure;

FIG. 2 shows the moldable covering placed on a windshield at thebeginning of a process of applying heat and pressure to a sacrificiallayer of the moldable covering;

FIG. 3 shows the moldable covering on the windshield at the end of theprocess of applying heat and pressure;

FIG. 4 shows the moldable covering on the windshield as the sacrificiallayer is being peeled off to reveal a stack of transparent lenses;

FIG. 5 shows the stack of transparent lenses after they have beentrimmed to fit the windshield; and

FIG. 6 shows an example operational flow according to an embodiment ofthe present disclosure.

DETAILED DESCRIPTION

The present disclosure encompasses various embodiments of a moldablecovering including a stack of two or more lenses and an installationmethod thereof. The detailed description set forth below in connectionwith the appended drawings is intended as a description of severalcurrently contemplated embodiments and is not intended to represent theonly form in which the disclosed invention may be developed or utilized.The description sets forth the functions and features in connection withthe illustrated embodiments. It is to be understood, however, that thesame or equivalent functions may be accomplished by differentembodiments that are also intended to be encompassed within the scope ofthe present disclosure. It is further understood that relational termssuch as first and second and the like are used solely to distinguish onefrom another entity without necessarily requiring or implying any actualsuch relationship in order between such entities.

FIG. 1 is schematic side view of a moldable covering 100 according to anembodiment of the present disclosure. The moldable covering 100 may beaffixed to a curved substrate 10 such as a windshield as part of theprocess of installing a stack of lenses 110 a, 110 b, 110 n(collectively lenses 110). The installed stack of lenses 110 may providethe substrate 10 with protection, tinting, thermal insulation, blockingultraviolet (UV) radiation, decoration, and/or the ability to peel awayand discard the outermost layer 110 n (and thereafter any newly revealedlayers 110) as needed during the lifetime of the product. In addition tothe lenses 110, the moldable covering 100 may include adhesive layers120 a, 120 b, . . . 120 n (collectively adhesive layers 120) providedrespectively on each lens 110, such that an adhesive layer 120 isinterposed between each pair of adjacent lenses 110 of the stack. On theoutermost lens 110 n of the stack of lenses 110, a sacrificial layer 130may be provided to allow for an improved process of installing the stackof lenses 110 to the substrate 10. The sacrificial layer 130 may includea sacrificial lens 132 and a sacrificial adhesive 134 interposed betweenthe sacrificial lens 132 and the outermost lens 110 n of the stack oflenses 110. When installing the stack of lenses 110, heat and pressuremay be applied to the sacrificial layer 130 to conform the stack oflenses 110 to the shape of the curved substrate 10. Thereafter, thesacrificial layer 130 may be peeled away to reveal the final product 140including the installed lenses 110.

If one were to only drape form the stack of lenses 110 on the curvedsubstrate 10 without the sacrificial layer 130, the process could resultin uneven heating or overheating as explained above, as well as thepossibility of permanently scratching the outermost lens 110 n with acard or squeegee. The inventor has found that these difficulties stemlargely from the lack of a female mold cavity to apply pressure as thestack of lenses 110 conforms to the male surface represented by thecurved substrate 10. As a result, neither heat nor pressure is evenlydistributed when the installer attempts to mold the stack of lenses 110to the curved substrate 10, resulting in the stated difficulties. Byproviding the sacrificial layer 130 to serve as the missing female moldcavity, the disclosed moldable covering 100 may overcome thesedeficiencies in at least two ways. First, the sacrificial layer 130 mayallow the installer to apply heat and pressure without fear ofscratching or otherwise damaging the end product. The sacrificial layer130 may simply be discarded along with any surface damage, while theunderlying outermost lens 110 n of the stack of lenses 110 remainsunblemished. Second, as heat and pressure are applied to the stack oflenses 110 through the intervening sacrificial layer 130, thesacrificial layer 130 may serve to distribute the heat and pressure overa wider area, resulting in a more even application of heat and pressureas the sacrificial layer 130 and underlying stack of lenses 110 togetherconform to the shape of the curved substrate 10.

The lenses 110 may comprise a transparent polyethylene terephthalate(PET) film such as a biaxially-oriented polyethylene terephthalate(BoPET) and may be fabricated from sheets of polyester film sold underthe registered trademark Mylar owned by the DuPont Company. Thethickness of each lens 110 may be between 0.5 mil and 7 mil (1 mil is0.001″), for example, 2 mil. Even after the adhesive material of theadhesive layers 120 is applied to a 2-mil thickness lens 110, thecombined thickness of the 2-mil thickness lens 110 and adhesive layer120 may still be 2 mil due to the adhesive layer 120 having only anominal thickness.

The adhesive used in the adhesive layers 120 may be applied, forexample, in selective areas around the periphery of the moldablecovering 100 as described in U.S. Pat. No. 6,536,045 to Wilson, issuedMar. 25, 2003 and entitled “Tear-off Optical Stack Having PeripheralSeal Mount,” the entire contents of which is expressly incorporatedherein by reference. The adhesive layers 120 may be made of a clearoptical low tack material and may comprise a water-based acrylicoptically clear adhesive or an oil-based clear adhesive. The adhesivelayer 120 a used to affix the moldable covering 100 to the substrate 10may be the same as or different from (e.g. stronger than) that of theadhesive layers 120 b, . . . 120 n interposed between each pair ofadjacent lenses 110 of the stack. A stronger adhesive may be used, forexample, in a case where individual lenses 110 are to be torn offwithout removing the entire stack of lenses 110 from the substrate 10during use. Along the same lines, the adhesive used for the adhesivelayers 120 b, . . . 120 n interposed between each pair of adjacentlenses 110 may be stronger than the sacrificial adhesive 134 of thesacrificial layer 130, such that the sacrificial layer 130 may be tornoff without removing the outermost lens 110 n from the stack of lenses110. The sacrificial adhesive 134 may similarly be a low tack materialand may comprise a water-based acrylic optically clear adhesive or anoil-based clear adhesive. However, in the case of the sacrificialadhesive 134, an opaque adhesive may be used instead since thesacrificial adhesive 134 is removed in the final product 140.

The lenses 110 may be optimized for scratch resistance and/or blocking(absorbing or reflecting) UV radiation. For example, an exterior side ofeach lens 110 may be deposited, sprayed, laminated, or otherwise coatedwith a coating (e.g. silicon ester acrylate oligomer and/or acrylatedurethane polyol) that is optimized for scratch resistance and/orblocking UV radiation as desired for properties suitable to the finishedproduct 140. These properties may be relaxed in the fabrication of thesacrificial layer 130, since the sacrificial layer 130 will not bepresent after the installation is complete. Thus, for example, thesacrificial layer 130 may be less scratch resistant than the outermostlens 120 n of the stack of lenses 120. Meanwhile, the sacrificial layer130 may be optimized for heat resistance, for example, coated with acoating (e.g. silicon ester acrylate oligomer and/or acrylated urethanepolyol) that is optimized for heat resistance, since the sacrificiallayer 130 may be heated directly as part of thermoforming the moldablecovering 100 to the shape of the curved substrate 10. Such heatresistance properties may be relaxed in the underlying stack of lenses100 as these lenses may only be subjected to the heat indirectly throughthe sacrificial layer 130. Thus, for example, the sacrificial layer 130may be more heat resistant than the outermost lens 110 n of the stack oflenses 100.

The sacrificial layer 130 may be made of a high temperature PET, forexample, one that is able to withstand temperatures between roomtemperature and 220° C. for two hours (e.g. without deteriorating). Thehigh temperature PET may be a clear BoPET, allowing for observation ofthe underlying stack of lenses 110 during the molding process, and may,for example, be a polyester film sold under the tradename Hostaphan RBBby the Mitsubishi Polyester Film Group. Such a high temperature BoPETmay be preferred when using hot air to heat the sacrificial layer 130during the molding process. Alternatively, the sacrificial layer 130 maybe made of an opaque (e.g. white) polyester film such as one sold underthe tradename Hostaphan WIN by the Mitsubishi Polyester Film Group. Suchan opaque polyester film may provide increased thermal uniformity whenusing infrared heaters to heat the sacrificial layer 130 during themolding process.

While the sacrificial layer 130 (e.g. the sacrificial lens 132 and/orthe sacrificial adhesive 134) may be optimized to withstand the heat ofthe installation process and to evenly distribute heat and pressure tothe underlying stack of lenses 110, it is generally unnecessary for thesacrificial layer 130 to meet the more stringent performance standardsof the underlying stack of lenses 110. For example, the stack of lensesmay be designed to meet federal standards for visible light transmission(e.g. 70%), such as may be set forth in the American National StandardsInstitute (ANSI) standards Z26.1-1966 and Z26.1a-1969, as well as toresist scratching (e.g. by windshield wipers) as described above and/orto absorb or reflect UV light to protect the lenses 110 from sun damage.By relaxing these requirements in the sacrificial layer 130, while atthe same time providing a more robust surface for applying heat andpressure without worry during installation, the moldable covering 100may allow for a more efficient method of installing the stack of lenses110. With the sacrificial layer 130 acting as a female mold cavity, thelayers of lenses 110 and adhesive 120 are held, form, and cure better tothe curved substrate 10 and never get scratched during the installationprocess.

FIG. 2 shows the moldable covering 100 placed on a windshield of a car20, the windshield serving as the substrate 10, at the beginning of aprocess of applying heat and pressure to the sacrificial layer 130 ofthe moldable covering 100. The moldable covering 100 may be adhered tothe windshield by a dry mount adhesive 120 a (see FIG. 1 ) as disclosed,for example, in U.S. Pat. No. 9,295,297 to Wilson, issued Mar. 29, 2016and entitled “Adhesive Mountable Stack of Removable Layers,” the entirecontents of which is expressly incorporated herein by reference.Alternatively, a wet mount adhesive 120 a may be used as disclosed, forexample, in U.S. Pat. No. 9,128,545 to Wilson, issued Sep. 8, 2015 andentitled “Touch Screen Shield,” the entire contents of which isexpressly incorporated herein by reference. Since the moldable covering100 may be flat (e.g. having been manufactured in a roll-to-rollprocess), the moldable covering 100 may not initially conform to thecurved shape of the windshield, resulting in regions of greater or lessadhesion and pockets/bubbles of air between the moldable covering 100and the windshield. Therefore, in order to conform the moldable covering100 to the shape of the windshield, heat and pressure may be appliedusing a heater 30 such as a hot air source (e.g. a heat gun or blowdryer) or an infrared heater. At the same time, pressure may be appliedto the moldable covering 100 using a card or squeegee. As the installerheats and presses down on the sacrificial layer 130 of the moldablecovering 100, the sacrificial layer 130 may shrink and stretch to takeon the contour of the opposing curved substrate 10 (the windshield) withthe stack of lenses 110 therebetween. In this way, the sacrificial layer130 may act as a female mold cavity to thermoform the underlying stackof lenses 110 to the shape of the windshield, evenly distributing theheat and pressure to shrink and stretch the lenses 110 to the correctshape and cure the adhesive layers 120.

FIG. 3 shows the moldable covering 100 on the windshield at the end ofthe process of applying heat and pressure. At this stage, the moldablecovering 100, including the sacrificial layer 130 as well as theunderlying lenses 110, is molded to the curved shape of the windshieldwithout air pockets/bubbles. The upper surface of the sacrificial layer130 may have various scratches and other blemishes caused by theinstaller as the installer applied pressure to the moldable covering 100using a squeegee or card. However, the underlying lenses 110 have beenprotected by the sacrificial layer 130 and are thus untouched.

FIG. 4 shows the moldable covering 100 on the windshield as thesacrificial layer 130 is being peeled off to reveal the stack oftransparent lenses 110. Remaining on the windshield is the final product140 (see FIG. 1 ) including the stack of lenses 110 and adhesive layers120. The final product 140 may meet performance standards as describedabove, including federal standards for visible light transmission (e.g.70%), as well as scratch resistance and/or UV absorption or rejection.The lenses 110 of the final product 140 may be accurately conformed tothe shape of the windshield and may be free of blemishes, even on theoutermost lens 110 n. The peeled off sacrificial layer 130 may simply bediscarded.

FIG. 5 shows the final product 140 including the stack of transparentlenses 110 after the stack of transparent lenses 110 has been trimmed tofit the windshield serving as the substrate 10. The stack of transparentlenses 110 may be trimmed using a knife such as a utility knife or boxcutter with a stainless-steel blade (a carbon blade may damage thewindshield). The trimming may be done after the sacrificial layer 130has been removed from the moldable covering 100 as shown in FIG. 5 ,such that only the revealed final product 140 is trimmed. Alternatively,the trimming may be done prior to the removal of the sacrificial layer130, once the moldable covering 100 has been conformed to the shape ofthe windshield as shown in FIG. 3 . In either case, the resultingtrimmed final product 140 may effectively be invisible as it matches theshape of the windshield beneath (though it may alter the coloring of thewindshield as in the case of window tinting).

FIG. 6 shows an example operational flow according to an embodiment ofthe present disclosure. The operational flow of FIG. 6 may serve as anexample method of installing the final product 140 including the stackof lenses 110 shown in FIG. 1 . First, the moldable covering 100,including both the final product 140 and the sacrificial layer 130, maybe placed on a curved substrate 10 such as the windshield of the car 20shown in FIG. 2 (step 610), with the adhesive layer 120 a on thewindshield and the sacrificial layer 130 facing outward away from thewindshield. For easier installation, the moldable covering 100 may berough cut (e.g. using an electric film cutter) so as not to extend toofar outside the windshield. The operational flow may continue withapplying heat and pressure to the sacrificial layer 130 of the moldablecovering 100 as described in relation to FIGS. 2 and 3 in order tothermoform the moldable covering 100 to the curved shape of thewindshield (step 620). After allowing the moldable covering 100 to cooldown, the operational flow may conclude with peeling off the sacrificiallayer 130 to reveal the final product 140 as described in relation toFIG. 4 (step 630) and performing a final trim as described in relationto FIG. 5 (step 640). As noted above, steps 630 and 640 may be performedin the order shown in FIG. 6 or in reverse order. The final product 140including the stack of lenses 110 is now uniformly formed and affixed tothe windshield surface.

In the example of FIG. 1 , three lenses 110 are shown. However, it iscontemplated for the moldable covering 100 to include a stack of four ormore lenses 110, or a stack of two lenses 110 or even a single lens 110,with the number of lenses 110 depending on the particular application.Counterintuitively, the inventor has found that a stack of multiplelenses 110 is easier to thermoform to a curved substrate 10 than a stackhaving a single lens 110.

Throughout this disclosure, the word “transparent” is used broadly toencompass any materials that can be seen through. The word “transparent”is not intended to exclude translucent, hazy, frosted, colored, ortinted materials.

The coatings described throughout this disclosure may be appliedaccording to known methods such as spin coating, dip coating, or vacuumdeposition.

The above description is given by way of example, and not limitation.Given the above disclosure, one skilled in the art could devisevariations that are within the scope and spirit of the inventiondisclosed herein. Further, the various features of the embodimentsdisclosed herein can be used alone, or in varying combinations with eachother and are not intended to be limited to the specific combinationdescribed herein. Thus, the scope of the claims is not to be limited bythe illustrated embodiments.

1. A method of installing a stack of two or more lenses on a curvedsubstrate, the method comprising: placing a moldable covering on acurved substrate, the moldable covering including a stack of two or morelenses, an adhesive layer interposed between each pair of adjacentlenses from among the two or more lenses, and a sacrificial layerdisposed on an outermost lens of the stack, the sacrificial layerincluding a sacrificial lens and a sacrificial adhesive interposedbetween the sacrificial lens and the outermost lens of the stack;applying heat and pressure to the sacrificial layer; and peeling off thesacrificial layer to reveal the stack of two or more lenses.
 2. Themethod of claim 1, wherein the curved substrate is a compound curvedsubstrate.
 3. The method of claim 2, wherein the curved substrate is awindshield.
 4. The method of claim 1, wherein the sacrificial layer ismore heat resistant than the outermost lens of the stack.
 5. The methodof claim 4, wherein the sacrificial layer is less scratch resistant thanthe outermost lens of the stack.
 6. The method of claim 1, wherein thesacrificial layer is less scratch resistant than the outermost lens ofthe stack.
 7. The method of claim 1, wherein the sacrificial lenscomprises a biaxially oriented polyethylene terephthalate film.
 8. Themethod of claim 7, wherein the biaxially oriented polyethyleneterephthalate film can withstand temperatures between room temperatureand 220° C. for two hours.
 9. The method of claim 1, wherein thesacrificial lens comprises an opaque polyester film.
 10. The method ofclaim 9, wherein the outermost lens of the stack comprises a transparentpolyethylene terephthalate film. 11-20. (canceled)